Reagents

About

From The Century Dictionary and Cyclopedia:

"n. One who or that which exerts reflex action or influence; an agency that produces reciprocal effects; a cause or source of counter-results.

n. In chem., a substance used to effect chemical change in another substance for the purpose of identifying its component parts or of ascertaining its percentage composition.

n. Anything used for the treatment of a substance under investigation to render its nature or condition more evident.

n. In experimental psychology: The observer in any form of psychological experiment: opposed to experimenter.

n. Same as reactor."